The present invention relates to methods of synthesis of betaine esters. More particularly, this invention concerns a method of synthesis of glycine betaine esters which utilizes environmentally acceptable raw materials and a process from which there is little or no waste.
Glycine betaine esters are an interesting and useful class of chemical compounds. A typical glycine betaine ester is: 
The chain length of the alcohol portion of the ester group, R, can be varied to provide a range of compounds. For the purposes of making betaine esters that will have biocidal and detergent activity the alcohols are derived from the reduction of oil and fat derived fatty acids from about C8 to C22, i.e.
CH3(CH2)nCH2OH
where n=6 to 20. The alcohols are esterified with glycine betaine:
The betaine esters are structurally similar to a widely used class of compounds, quaternary ammonium halides, which are used as sanitizing biocides, surface sterilizing agents, fabric softeners and cationic surface-active agents (surfactants). A number of commercially available quaternary ammonium halides are available for these purposes from chemical suppliers such as Rohm America Inc. or Lonza Inc. The synthesis and uses of quaternary ammonium halides are well known, for example see Kirk-Othmer Encyclopedia of Chemical Technology, Fourth Edition. Quaternary ammonium halides, however, are quite toxic and persist in the environment after use.
Researchers at the University of Goteberg in Sweden determined that the glycine betaine esters were a superior substitute for the quaternary ammonium halides. The methods of synthesis for the glycine betaine esters has been quite difficult. Some of these methods are given in U.S. Pat. No. 4,020,100 and U.S. Pat. No. 4,076,743. Expensive and toxic reagents are used to produce these glycine betaine esters. The available synthetic methods relied on the use of a complicated and costly preparation. Most of the methods start with chloroacetic acid and add the cetyl alcohol group as an ester to the chloroacetic acid. The final step in these earlier betaine esters processes is replacing the chlorine with an adduct from trimethylamine.
It is proposed to produce glycine betaine esters conveniently, economically with a process from which there is little or no waste. Additionally the raw materials used during the synthesis would be environmentally acceptable and pose little risk.
In one aspect the present invention relates to a new environmentally friendly method of synthesis of betaine esters performing the esterification directly.
In another aspect of this instant invention all by-product streams can be either recycled or rendered harmless.